Preparation:1. Preheat the oven to 350° (If you are using a dark or nonstick pan, reduce the heat by 25° F). Grease and flour a tube pan with a removable bottom, making sure to tap out excess flour.2. In a large bowl, combine the apple slices, cinnamon and sugar. Toss together gently, making sure the apples are well coated with the cinnamon and sugar, and set aside.3. In another large bowl, whisk together the flour, sugar, baking powder, and salt. Add the oil, eggs, orange juice, and vanilla, and beat just until smooth. The batter will be very thick.4. Pour about 1/3 of the batter into the prepared tube pan. If necessary, use a spatula to spread the batter so it covers the bottom of the pan. Layer about 1/3 of the apple slices over the batter. Repeat with another layer of batter, then apples, then batter.5. Arrange the final layer of apples decoratively in concentric circles over the batter, overlapping the apple slices slightly (they will spread out as the cake bakes). Drizzle the cake with a bit of the remaining cinnamon sugar “syrup” from the apple bowl.6. Place the cake on a cookie sheet or on top of a piece of foil to catch any drips, and bake in the center of the preheated oven for 1 1/2 to 1 3/4 hours, or until a tester comes out clean and the top of the cake has a golden “crust.”7. Allow the cake to cool in the pan on a wire rack. When cool, run a knife or spatula around the edge of the pan, and remove the outside of the cake pan. Gently run a knife or spatula between the cake and the pan bottom to loosen. Invert the cake over a plate and remove the pan bottom (the cake will be upside down on the plate.) Place a cake plate face down on the bottom side of the cake, and holding both plates, flip the cake, so it is right-side (apple-side) up. Enjoy!